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Hbc 100 Medical Biochemistry Question Paper

Hbc 100 Medical Biochemistry

Course:Bachelor Of Medicine And Bachelor Of Surgery

Institution: Moi University question papers

Exam Year:2008

M O I U N I V E R S I T Y

SCHOOL OF MEDICINE
END OF YEAR EXAMINATION (EYE) 2007/2008
COURSE TITLE: BIOCHEMISTRY
COURSE CODE: MBC 100
PROGRAMME: M.B.Ch.B. YEAR OF STUDY: 1 (ONE)
DATE: 4TH NOVEMBER, 2008 TIME: 9.00 A.M. – 12.00 NOON

GENERAL INSTRUCTIONS:-

(I) WRITE YOUR UNIVERSITY REGISTRATION NUMBER ON EVERY PIECE OF PAPER YOU USE.

(II) DO NOT WRITE YOUR NAME(S) ON ANY PIECE OF PAPER YOU USE.

(III) THIS PAPER CONSISTS OF THREE (3) SECTIONS, HEADED: SECTION I: THIRTY (30) MULTIPLE CHOICE QUESTIONS (MCQS) TO BE ANSWERED IN SIXTY (60) MINUTES; SECTION II: SIX (6) SHORT ANSWER QUESTIONS (SAQS) TO BE ANSWERED IN SIXTY (60) MINUTES AND SECTION III: THREE (3) LONG ESSAY QUESTIONS (LEQS) TO BE ANSWERED IN SIXTY (60) MINUTES.

(IV) THE QUESTIONS ARE SET OUT IN THREE (3) SECTIONS HEADED SECTION I: MCQS, SECTION II: SAQS AND SECTION III: LEQS.

(V) READ CAREFULLY THE ADDITIONAL INSTRUCTIONS PRECEEDING EACH SECTION.

SECTION I: MULTIPLE CHOICE QUESTIONS (MCQs)
(60 Minutes)

TYPE III

INSTRUCTIONS:-

(I) EACH OF THE QUESTIONS IN THIS SUBSECTION CONSISTS OF A STATEMENT/QUESTION WHOSE MOST APPROPRIATE COMPLETION/ANSWER IS PROVIDED AMONG THE FIVE OPTIONS NUMBERED (a) - (e).

(II) FOR EACH QUESTION, SELECT THE MOST APPROPRIATE OPTION AND INDICATE BY PRINTING AN X IN THE APPROPRIATE BOX IN THE ANSWER SHEET PROVIDED.

(III) A CORRECT RESPONSE EARNS YOU TWO MARKS.

1. Most enzyme catalyzed reactions occur in:

a) Picoseconds.
b) Nanoseconds.
c) Microseconds.
d) Milliseconds.
e) Seconds.

2. Which of the following is not an appropriate description of a polysaccharide?

a) They contain ?-1, 6-glycosidic bonds.
b) They contain branched sugar chains.
c) They can be digested by humans.
d) They are storage forms of energy in yeast and bacteria.
e) They are storage forms of energy in humans.

3. Which of the following statements is correct about ?-helix structure of protein?

a) It is maintained by hydrogen bonds contributed by side chain of amino acids.
b) It makes up about the same percentage of all proteins.
c) It is stabilized by hydrogen bonds between an amino acid and a COOH group.
d) It can influence solubility of amino acids.
e) It is found in all 20 amino acids at equal frequencies.

4. Which of the following amino acids will alter the direction of polypeptide chains and interrupt ?- helices?

a) Phenylalanine.
b) Cysteine.
c) Tryptophan.
d) Histidine.
e) Proline.

5. DNA polymerase I activity requires all of the following except:

a) Mg++.
b) ATP.
c) dGTP.
d) dCTP.
e) A template.

6. The DNA – dependent RNA polymerase reaction that produces a RNA transcript requires all of the following except:

a) ATP.
b) Promotor sequence.
c) Terminator sequence.
d) DNA.
e) Operator sequence.

7. All of the following are characteristics or functions of tRNA except that:

a) It contains a codon.
b) It contains an anticodon.
c) It can become covalently attached to amino acid.
d) It serves as an adapter between mRNA and amino acid.
e) It can have any number of different amino acid sequences.

8. Which of the following is not a precursor or intermediate in heme synthesis?

a) Glycine.
b) d-Aminolevulinic acid.
c) Porphobilinogen.
d) Biliverdin.
e) Succinyl CoA.

9. Hb differs from Mb in the following ways except:

a) Hb is multimeric whereas Mb is monomeric.
b) Hb binds O2 more tightly than does Mb.
c) Hb binds CO2 more effectively than does Mb.
d) Hb consists of 4 polypeptide chains whereas Mb has one.
e) Binding of O2 by Hb depends on CO2 whereas binding of O2 by Mb does not.

10. The structure of deoxyhemoglobin is stabilized by each of the following interacations except for:

a) Coordination of the hemes with distal histidine.
b) Bishosphoglycerate binding.
c) Salt bridges between acidic and basic side chains.
d) Hydrophobic interactions.
e) Salt bridges involving N-terminal carbamates.

11. Which of the following statements is incorrect? HbS forms fibrous precipitates:

a) Because valine at position 6 forms sticky hydrophobic patch.
b) That are reversible upon oxygenation.
c) That distort the shape of red cells.
d) Only in deoxy form.
e) Only in homozygotes.

12. The molecular defects in HbS and thalassemia are similar in that the defect:

a) Occurs outside of the DNA encoding the protein.
b) Results in a stop codon that produces a short protein.
c) Results in the substitution of one amino acid for another.
d) Occurs within the structural genes.
e) Results from the deletion of the gene encoding the protein.

13. Which of the following characteristics is typical for steroid hormones especially aldosterone?

a) It has 18 carbon atoms.
b) It is a C-19 ketosteroid.
c) It contains an aldehyde group at C-18.
d) It contains an aromatic ring.
e) It has two OH groups.

14. Which of the following statements about DNA ligase is incorrect?

a) It forms a phosphodiester bond between OH and PO4 groups.
b) It requires NAD+ or ATP as a source of energy.
c) It is involved in DNA replication and repair.
d) It catalyzes a reaction involving adenylate enzyme.
e) It catalyzes a reaction involving activation of DNA.

15. Which of the following is not a function or component of VLDL?

a) They contain apoprotein B-100.
b) They are transporters of cholesterol.
c) They are precursors of LDL.
d) They are transporters of triglycerides.
e) They are degraded by lipoprotein lipase.

16. Which of the following statements about the active form of vitamin D is incorrect?

a) It has the same fused ring as cholesterol.
b) It requires hydroxylation to form cholecalciferol.
c) It is important in calcium and phosphorus metabolism.
d) It can be synthesized from cholesterol.
e) It can be obtained from the diet.

17. Which statement about recombination of retroviral DNA with host DNA is correct?

a) It requires involvement of NADPH.
b) It occurs in specific sites of the host genome.
c) It requires ATP hydrolysis.
d) It involves the duplication of 4 to 6 nucleotides.
e) It requires phosphorylation of viral DNA.

18. Which of the following functions of rifampicin is correct?

a) It interacts with DNA template.
b) It inhibits elongation step of RNA synthesis.
c) It prevents initiation step of RNA synthesis.
d) It inhibits RNA polymerase.
e) It protects promoters from hydrolysis.

19. Which of the following statements about aminoacyl-tRNA synthetase reaction is incorrect?

a) It uses ATP as a cofactor.
b) It contains B sheet domains at its active site.
c) It activates the amino groups of amino acids.
d) It forms an acyl ester bond.
e) It forms a mixed anhydride linkage with AMP.

20. Proteoglycans are best described as:

a) Extracellular secretions conjugated to N-acetylgalactosamine.
b) Complex mixtures of heteropolysaccharides and proteins.
c) Glycoproteins conjugated to N-acetylglucosamine.
d) Fibrous proteins consisting of three polypeptide chains.
e) Structural proteins found in lungs and blood vessels only.

21. Which of the following sugars is present in glycoproteins?

a) Ribose.
b) Ribulose.
c) Xylulose.
d) Xylose.
e) Deoxyribose.

22. Which of the following is not a function of folic acid?

a) Synthesis of amino acids.
b) Synthesis of coenzyme A.
c) Prevention of neural tube defects.
d) Prevention of anemia.
e) Production of new DNA.

23. The structure of deoxyribonucleic acid does not have:

a) Adenine.
b) Cytosine.
c) Uracil.
d) Guanine.
e) Thymine.

24. Which of the following enzymes is not involved in DNA replication?

a) DNA ligase.
b) DNA polymerase.
c) DNA-dependent RNA polymerase.
d) Helicase.
e) Topoisomerase.

25. Which of the following fatty acids has the highest melting point?

a) Cerebronic.
b) Lignoceric.
c) Arachidonic.
d) Linolenic.
e) Stearic.

26. Which of the following is transported by ceruloplasmin in blood?

a) Iron.
b) Manganese.
c) Copper.
d) Zinc.
e) Calcium.

27. Vitamin B5 is also known as:

a) Thiamine.
b) Riboflavine.
c) Pantothenic acid. *
d) Pyridoxine.
e) Niacin.

28. RNA synthesis is initiated by RNA polymerase binding to:

a) An initiator codon.
b) A RNA primer.
c) A transcription loop.
d) A promoter site.
e) A growing RNA chain.

29. Carbon dioxide is transported by:

a) Myoglobin.
b) Hemoglobin.
c) Hb and Bohr effect phenomenon.
d) Diffusion.
e) Fe++ in heme group.

30. Cerebron is made up of all of the following except:

a) Serine.
b) Choline.
c) Fatty acid.
d) Sphingosine.
e) Galactose.

SECTION II: SHORT ANSWER QUESTIONS (SAQs) (60 Minutes)

INSTRCUTIONS:

I) THERE ARE SIX (6) QUESTIONS IN THIS SECTION.

II) ANSWER ALL THE SIX (6) QUESTIONS.

III) START EACH QUESTION ON A FRESH PIECE OF PAPER OF THE BOOKLET.

SAQ 1. Describe the three (3) main physical properties of fatty acids.

SAQ 2. Describe the structure and functions of tRNA.

SAQ 3. Describe the general functions of plasma and mucin glycoproteins.

SAQ 4. Differentiate between the 1st order, mixed order, and zero order kinetics of enzyme-catalyzed reactions.

SAQ 5. Distinguish between sucrose and lactose from the structural standpoint and their natural occurrences.

SAQ 6. Distinguish between hemoglobin and myoglobin from their structural and functional standpoints.

SECTION III: LONG ESSAY QUESTIONS (LEQs)
(60 Minutes)

INSTRUCTIONS:

I) THERE ARE THREE (3) QUESTIONS IN THIS SECTION.

II) ANSWER ALL THE THREE (3) QUESTIONS.

III) START EACH QUESTION ON A FRESH PIECE OF PAPER OF THE BOOKLET.

LEQ 1. Describe the following structural organization of proteins:

a) The primary structure.
b) The secondary structure.
c) The tertiary structure.
d) Quaternary structure.

LEQ 2. Outline the biosynthesis of cortisol and aldosterone.

LEQ 3. Describe a sequence of reactions leading to the biosynthesis of heme.

Hbc 100 Medical Biochemistry Question Paper

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